Motors account for a major proportion of total power consumption. Since the preservation of global environment is demanded, higher efficiency and labor savings are inevitable problems to be pursued.
As a solution for higher efficiency of motors, the improvement of coil space factors of stator windings has been constantly pursued as the most significant object in the development of winding methods.
Referring to FIG. 5, a conventional winding method will be described below.
A nozzle winding method of in-slot nozzle oscillation winding is in the mainstream of conventional winding methods. In this method, when concentrated windings are provided directly on magnetic poles 12 which are disposed radially in a stator core 10 in an integrated manner, a nozzle 41 is inserted, from the inside of the stator core 10, into a slot 15 formed by the adjacent magnetic poles 12 and magnetic pole protrusions 13, and winding is performed while the nozzle 41 is rotated around the magnetic pole 12.
Although the nozzle winding method achieves high-speed winding with ease, winding cannot be performed in a nozzle passage area 16 in the slot 15 and thus the coil space factor of winding cannot be improved more than a certain degree.
As a conventional method of winding in the nozzle passage area 16, a method of combining insertion winding and nozzle winding is known in which winding is not performed directly (e.g., Japanese Patent Laid-Open No. 2002-142416). With this method, two coils are formed and combined by using the two methods, thereby achieving windings utilizing all effective slot areas.
Further, a winding method not causing a nozzle to pass through a slot is also known (e.g. Japanese Patent Laid-Open No. 2000-270524 or Japanese Patent Laid-Open No. 2001-103716). According to this method, winding can be performed without the necessity for the nozzle 41 to enter the slot 15 and thus winding can be performed in the nozzle passage area 16 during nozzle winding. Further, the size of the nozzle becomes less limited and it becomes possible to perform multiple winding for supplying a plurality of conductors at a time.